Two secret government reports reveal a massive area of Western Australia's outback can no longer sustain traditional grazing, which could force more people off the land.

Opposition environment spokesman Chris Tallentire secured the two Department of Agriculture and Food WA reports through the state's Freedom of Information laws and released an analysis on Tuesday.

The leaked documents suggest ever-increasing amounts of WA pastoral land are becoming unsuitable for grazing. Credit:Glenn Campbell

Report data showed an area of WA - equivalent to 14 times the size of Tasmania - had been in decline for decades. Less than one in four pastoral properties from the Pilbara south to the Nullarbor were still capable of sustaining grazing.

"This is the wake-up call that had to happen. The heart of our great state, the story of who we are as West Australians, is at stake," Mr Tallentire said.